[camperman]

Because it's so easy. From the manual:

So here's something to pop up a message box on Windows:

    local ffi = require("ffi")

    ffi.cdef[[

        int MessageBoxA(void *w, const char *txt, const char *cap, int type);

    ]]

    ffi.C.MessageBoxA(nil, "Hello world!", "Test", 0)

Bing! Again, that was far too easy, no?

Compare this with the effort required to bind that function using the classic Lua/C API: create an extra C file, add a C function that retrieves and checks the argument types passed from Lua and calls the actual C function, add a list of module functions and their names, add a luaopen_* function and register all module functions, compile and link it into a shared library (DLL), move it to the proper path, add Lua code that loads the module aaaand ... finally call the binding function. Phew!

[spc476]

I did write a Lua binding to TCC [1] and used that to write a Lua module to load Lua modules written in C directly from source code [2], which I used in an older version of my JSON decoder [3], which contains the C code embedded right in the Lua source code.

On the down side, TCC doesn't support all the architectures I use, so I mostly use it for proof-of-concept and throw away code.

One thing I keep thinking is to possibly use TCC (or parts of it) to parse C header files directly, so it would be easier to use an FFI in Lua.

[1] https://github.com/spc476/lua-conmanorg/blob/master/src/tcc....

[2] https://github.com/spc476/lua-conmanorg/blob/master/lua/cc.l...

[3] https://github.com/spc476/LPeg-Parsers/blob/json-1.0.0/json....

[sillysaurus3]

In fairness, luaffifb seems to give the same feature.

I think the main argument against Lua + luaffifb is that it might require an external dependency: luarocks. Whereas if someone were to theoretically provide Lua integration with emacs, it might be a good idea to offer the ffi library as a baseline feature.

This is a weak argument, because it should be possible to embed luaffifb plus Lua inside of a linked library, with no need to depend on luarocks.

It's probably best to explore both options.

[shalabhc]

Well, LuaJIT will also JIT compile Lua code operating on C structures - so speed could be another big argument.

[daurnimator]

As I linked in the above post, the ffi is available for normal lua too: it's not exclusive to LuaJIT